Field of Invention
The present invention relates to a debris filter apparatus configured to be attached to a shroud of a turbine vane to prevent clogging of downstream turbine vane cooling holes while still allowing adequate air flow to the cooling holes.
Description of Related Art
A typical gas turbine engine includes a compressor for compressing air, a combustor for mixing the compressed air with fuel, and a turbine assembly, with alternating rows of vanes and blades, for producing power. A first row of turbine vanes is exposed to hot gas temperatures in excess of the melting point of the vane material. Various cooling techniques are used to ensure that the maximum metal temperature does not exceed the melting point. One of these cooling techniques involves flowing relatively cool air from the compressor through an array of holes in the turbine vane. The cooling air from the compressor may include debris such as dirt, rust, and insulation, for example. The debris can accumulate within and clog the cooling holes in the vane. Clogging can result in vane material oxidation, and may require vane replacement prior to a scheduled service interval.
Prior art approaches include filtration systems located at an inlet of the engine. However, since debris that blocks the cooling holes of the turbine vane may be generated within the engine itself, the benefit of these approaches are limited. Another prior art approach to prevent clogging of turbine vane cooling holes involves strategic drilling of the cooling holes. This may result in extended use intervals before the vane holes clog, without substantially increasing coolant flow rate. For example, as described in U.S. Pat. No. 5,062,768, intersecting cylindrical holes are drilled such that the flow constriction is located at the point of intersection and the holes overlap to form a single outlet larger than that which would result from either hole individually. Another prior art approach to prevent clogging of turbine vane cooling holes involves use of a device embedded in the turbine vane itself. For example, as described in U.S. Pat. No. 8,176,720, a centrifugal particle separator is embedded within a platform (or root) of a turbine blade or shroud(s) of a turbine vane to remove dirt and dust particles from the compressed cooling air.
Additional prior art approaches, for example, as described in US Patent Application Nos. 2007/0048122, 2009/0214329 and 2013/0192257 pertain to the application of a filter to cooling flow through a blade outer air seal (also referred to as a “ring segment”). More specifically, US Patent Application No. 2007/0048122 describes an individual filter integrated into the blade outer air seal for each cooling hole, US Patent Application No. 2009/0214329 describes a filter placed immediately outside and upstream of the impingement cavity of the blade outer air seal, and US Patent Application No. 2013/0192257 describes a filter placed immediately upstream of one or more cooling holes in a turbine shroud hanger (also referred to as an “isolation ring”) that feeds cooling flow to the blade outer air seal.
These prior art approaches are prone to starvation of the vane cooling holes caused by filter clogging.
It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed.